British Prime Minister David Cameron, visiting with top Turkish officials in a two-day visit to Ankara, is expected to press for greater cooperation in stopping jihadists from joining the Islamic State group.

International relations expert Cengiz Aktar of Istanbul’s Suleyman Sah University said the jihadist threat is of particular concern to the British.

Anti-terrorist collaboration "is very, very important," he said. "There are many fighters of British nationality among the ranks [of] ISIS. For sure, the intelligence units of the UK are following this very closely."

British intelligence is already reportedly working with its Turkish counterparts on stopping people from joining IS. But Ankara is under pressure from London to do more to stop jihadists from using Turkey as a highway to join Islamic State forces in neighboring Iraq and Syria, as well as assist in tracking jihadists seeking to return home.

Diplomatic columnist Semih Idiz of the Turkish newspaper Taraf and Al Monitor website said relations were further strained between the two countries after allegations surfaced that Turkey had handed over two British citizens to IS in return for Turkish hostages who were captured by the terrorist organization in June.

"There are some issues about some detainees released by Turkey who were within the Mosul hostage exchange recently. ... There are some questions that the British side is raising on this," Idiz said.

Cameron’s efforts to press for further cooperation are likely to be met with a call from Turkey’s political leaders for support of their demands on Syria. Turkish President Recep Tayyip Erdogan, while visiting Lithuania Tuesday, reiterated his call for the creation of safe havens protected by no-fly zones in Syria in exchange for the opening of Turkey’s bases to anti-Islamic State coalition forces.

Turkey’s bid to join the European Union could complicate Cameron’s visit. The UK's traditional strong backing of Ankara's EU bid was the foundation of strong bilateral relations. But analyst Aktar said London is no longer viewed so positively in Ankara.

"The Brits used to be the main supporters of Turkey," he said. "Unfortunately, no more. They are very neutral when it comes to Turkey’s EU relations."

The UK has been among the targets of Erdogan’s increasingly anti-West rhetoric, resurrecting historical Turkish fears of British spies. "Under every stone can be found an English spy" is an old Turkish adage, and a popular Turkish soap opera recently involved a plot against Turkey by a British prince.

Also, the security barriers protecting the British Embassy, where Cameron is staying, were removed by Turkish authorities without explanation last week.